Pen



FIG. 1. is a top perspective view of the pen;

FIG. 2. is a top view of the pen;

FIG. 3. is a bottom view of the pen;

FIG. 4. is a left side view of the pen;

FIG. 5. is a right side view of the pen;

FIG. 6. is an front end view of the pen; and,

FIG. 7. is a rear end view of the pen.

The portions of the pen shown in broken lines illustrate environmental matter and form no part of the claimed design. 

The ornamental design for a pen, as shown and described. 